When fuel is gas, the dynamic range of the required injection amount is large compared to the case of liquid. Therefore, when a large injection valve that can inject the maximum value of the presumed required injection amount within a predetermined time is used as an injection valve injecting a gas fuel, the injection amount cannot be controlled precisely when the required injection amount is small.
Therefore, the fuel injection system described in Patent Literature 1 includes two injection valves of a small injection valve of a low flow rate type and a large injection valve of a high flow rate type. Also, by controlling the electric actuators provided in the respective injection valves as described below, control from a large injection amount to a small injection amount is allowed. More specifically, in the range of a small required injection amount, the injection amount is controlled by flow rate control by the small injection valve while the large injection valve is totally closed. Also, in the range of a large required injection amount, the injection amount is controlled by flow rate control by the large injection valve while the small injection valve is totally opened.
However, according to the above system described in Patent Literature 1, electronic control of the operation of the electric actuators is required for each of the two injection valves. Therefore, the control becomes complicated, and processing load of the control increases.